Signal detection and interference cancellation based on simplified matrix inversion for CDMA applications

Claim 1

An information processing system for detecting a spreaded signal having information from a plurality of users in a CDMA system, comprising: a receiving processor, having a demodulating element connected and configured to convert said spreaded signal into a baseband signal, at least one multiplier connected and configured to despread said baseband signal to produce a despreaded signal corresponding to one user, an integrating element corresponding to said at least one multiplier and operating to integrate said despreaded signal by first and second integration times to respectively produce first and second integrated signals; a digitization module comprising first and second digitizers connected to said integrating element to respectively sample and digitize said first and second integrated signals into first and second digital signals respectively indicative of said first and second integrated signals; and a digital detector connected to receive said first and second digital signals and configured to digitally process said first and second digital signals to produce a digital output indicating information from said one user and to substantially remove interference noise caused by signals from other users based on cross correlation of different users.

Claim 5

A method for reducing interference of cross correlation of user signals from different users in a CDMA system, comprising: sampling a received signal imprinted with said user signals to obtain a demodulated signal; processing said demodulated signal according to a first correlation operation to produce despreaded signals respectively corresponding to different users by using predetermined codes; performing a first integration for a first integration time on each despreaded signal to produce a first integrated signal and a second integration for a second integration time on each despreaded signal to produce a second integrated signal; sampling and digitizing said first and second integrated signals to produce first and second digital signals for each despreaded signal; processing said first and second digital signals corresponding to each despreaded signal with a second correlation operation according to an operating condition of said CDMA system to reduce interference noise in said first and second digital signals; and performing a plurality of recursive operations of said second correlation to reduce said interference noise below a desired level.

Claim 6

A method for reducing interference of cross correlation of user signals from different users in a CDMA system, comprising: sampling a received signal imprinted with said user signals to obtain a demodulated signal; processing said demodulated signal according to a first correlation operation to produce despreaded signals respectively corresponding to different users by using predetermined codes; performing a first integration for a first integration time on each despreaded signal to produce a first integrated signal and a second integration for a second integration time on each despreaded signal to produce a second integrated signal; sampling and digitizing said first and second integrated signals to produce first and second digital signals for each despreaded signal; processing said first and second digital signals corresponding to each despreaded signal with a second correlation operation according to an operating condition of said CDMA system to reduce interference noise in said first and second digital signals; and performing a plurality of recursive operations of said second correlation to reduce said interference noise below a desired level.

Claim 9

A method for reducing interference noise in detection of transmitted symbols of a plurality of users in a CDMA system, comprising: demodulating and converting a CDMA signal imprinted with said transmitted symbols from said users into a baseband signal; despreading said baseband signal into a plurality of user signals respectively corresponding to said users; respectively integrating each user signal for a first integration period to produce a first integrated user signal and for a second integration period to produce a second integrated user signal; converting said first and second integrated user signals into first and second digital user signals for each of said users; forming a user signal array, y, with said first and second digital user signals from each of said users, wherein a number of elements in said user signal array y is twice of a number of said users; forming a symbol array, z, with said transmitted symbols that are to be determined, wherein said user signal array y and said symbol array z are associated with each other by a matrix R according to a relationship of y=R z; performing a digital matrix inversion process to determine an inverse matrix R -1 of said matrix R so that said interference noise is reduced; and determining said transmitted symbols from said users by using a relationship of z=R -1 y.

Claim 10

A method for reducing interference noise in detection of transmitted symbols of a plurality of users in a CDMA system, comprising: demodulating and converting a CDMA signal imprinted with said transmitted symbols from said users into a baseband signal; despreading said baseband signal into a plurality of user signals respectively corresponding to said users; respectively integrating each user signal for a first integration period to produce a first integrated user signal and for a second integration period to produce a second integrated user signal; converting said first and second integrated user signals into first and second digital user signals for each of said users; forming a user signal array, y, with said first and second digital user signals from each of said users, wherein a number of elements in said user signal array y is twice of a number of said users; forming a symbol array, z, with said transmitted symbols that are to be determined, wherein said user signal array y and said symbol array z are associated with each other by a matrix R according to a relationship of y=R z; performing a digital matrix inversion process to determine an inverse matrix R -1 of said matrix R so that said interference noise is reduced; and determining said transmitted symbols from said users by using a relationship of z=R -1 y.